Fin

ABSTRACT

An object of the present invention is to provide fin in which the fin can be easily attached or detached to a board, its attached state can be maintained well, and the fin readily comes off in an emergency such as when the fin is brought into contact with human body. 
     Furthermore, it is an object of the present invention to allow the reduction of rattle when the fin is attached. 
     To solve such problems, provided is a fin, comprising a hollow part at a side surface of an attachment base portion of the fin to be attached to a groove in a bottom surface of a surfboard, 
     wherein a ball part is biased outwardly of the hollow part by an elastic member in the hollow part; and 
     wherein the ball part in the hollow part of the attachment base portion of the fin is moved into the hollow part against a biasing force from the elastic member, and thus the fin is detachably mounted in the attachment groove of this board under elastic compression force.

TECHNICAL FIELD

The present invention relates to a fin of a surfboard and, more specifically, to a fin that can be detachably attached to the surfboard, the fin readily coming off in an emergency such as when the fin hits against human body.

BACKGROUND ART

Conventionally, there have been roughly two types of fin attachment structures of a surfboard: a fixed fin type; and a detachable fin type.

In this case, the detachable fin type, as compared to the fixed fin type, is used more frequently and there are various attachment structures because it allows the attachment of a fin in an arbitrary shape according to a user's preference and the fin can be detached and carried.

That is, a fin box and the like are arranged in advance on the bottom surface of a surfboard by embedding it and then the fin is detachably mounted in the fin box.

In this case, what has structures of screwing fixing as structures that allow a fin to be detachable when the fin is broken or carried include those disclosed in Japanese Unexamined Patent Publication (Kokai)No. H6-255575 (patent document 1), Translated Japanese Publication of Patent Application No. 2001-520961 (patent document 2), Translated Japanese Publication of Patent Application No. 2002-530242 (patent document 3), and Japanese Unexamined Patent Publication (Kokai) No.2003-306195 (patent document 4).

These have a structure in which screws, bolts or the like are used to fasten a fin for fixing the fin to the fin box.

In addition to the above, structures in which grooves having various structures are provided in the fin box and the fin is fastened by fitting the fin into the groove include those disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2005-74026 (patent document 5), Japanese Unexamined Patent Publication (Kokai) No. 2005-112206 (patent document 6), and Japanese Unexamined Patent Publication (Kokai) No. 2006-280839 (patent document 7).

Further, as a structure in which the fin is fastened using a C-shaped clamp, there is one disclosed in Translated Japanese Publication of Patent Application No. 2003-528003 (patent document 8).

In addition to the above, structures in which the fin is fastened so that it can be attached detachably using a special locking member include those disclosed in Translated Japanese Publication of Patent Application No. 2005-508798 (patent document 9) and Translated Japanese Publication of Patent Application No. 2005-526664 (patent document 10).

Furthermore, as a structure in which both the fin box and the fin fitted therein have a fitting structure in a special shape and thus the fin is fastened detachably, there is the one disclosed in Japanese Unexamined Patent Publication (Kokai) No.2007-160969 (patent document 11).

Patent document 1: Japanese Unexamined Patent Publication No. H6-255575

Patent document 2: Translated Japanese Publication of Patent Application No. 2001-520961

Patent document 3: Translated Japanese Publication of Patent Application No. 2002-530242

Patent document 4: Japanese Unexamined Patent Publication (Kokai) No. 2003-306195

Patent document 5: Japanese Unexamined Patent Publication (Kokai) No. 2005-74026

Patent document 6: Japanese Unexamined Patent Publication (Kokai) No. 2005-112206

Patent document 7: Japanese Unexamined Patent Publication (Kokai) No. 2006-280839

Patent document 8: Translated Japanese Publication of Patent Application No. 2003-528003

Patent document 9: Translated Japanese Publication of Patent Application No. 2005-508798

Patent document 10: Translated Japanese Publication of Patent Application No. 2005-526664

Patent document 11: Japanese Unexamined Patent Publication (Kokai) No. 2007-160969

DISCLOSURE OF THE INVENTION

As described above, there exist various attachment structures as to a fin of a surfboard.

First, the structure disclosed in patent document 1 adopts so-called screw fixing, in which a screw is screwed up, or the fin can be detached by unscrewing the screw.

Because of this, attachment and detachment of the fin require a special tool, such as a screwdriver.

Further, for example, when the fin comes into contact with human in use, the fin will remain fastened and human body may be damaged, that is, it is unlikely that the fin comes off the board to prevent the fin from damaging human in such an emergency.

Next, in the structures disclosed in patent document 2, patent document 3, and patent document 4, a fin is screwed up in the transverse direction and detachment of the fin similarly requires a special tool such as a screwdriver, and, for example, even if the surfer falls during surfing and the fin of the surfboard comes into contact with human body, the fin will remain fastened thereto and there is a possibility that the fin may damage human body.

Further, the structures shown in patent document 5 and patent document 6 are those in which a fin is inserted along a groove and fastened to a predetermined position, and can be tightly attached, thus being hard to come off.

That is, the structure is not classified as the group of screw fixing, but on the other hand, the fin is tightly inserted in the recess portion in order to prevent the fin from dislodging unnecessarily when in use and fixed in place in the groove.

As a result, the fin is tightly fitted thereto in order to prevent its dislodgement, and thus it is unlikely that the fin readily comes off the board just by the impact in the case of a collision etc.

That is, under this impact, the fin comes off only when this impact is applied in a specifically particular direction; and even if it is the impact from the direction to which the fin comes off, the fin just moves a little and will stop after movement, so that the damage to the human body from the fin at the time of contact cannot be prevented.

Next, as to patent document 7, the fin is similarly inserted into the groove, and moved along the groove to be attached.

In this case, it is necessary to attach or detach the fin in accordance with the insertion procedure, and further, for an unexpected impact, the fin is unlikely to come off when in use as long as the fin does not suffer an impact from one extremely specified direction.

Consequently, when the fin comes into contact with human body, there is a high possibility that the fin remains attached to the board as it is and the human body is damaged.

Next, in the configuration shown in patent document 8, the C-shaped clamp is used to fasten the fin to the fin box as a locking member, that is, the fin is tightly fitted to the clamp in the so-called fin box, and a large force is required to detach the fin and at the same time, it is difficult to detach the fin unless the fin is pulled out in a given direction of the fin box.

Consequently, such an impact that is applied when the fin comes into contact with human when in use of the surfboard or an impact in a certain direction will not cause the fin to come off and therefore the fin remains fastened thereto.

Further, there arises another need, such as that the accuracy at the time of attachment is required, that is, at least the slot must be matched or the fin must be inserted tightly into the clamp.

According to patent document 9, a cam is rotated by the worm gears and thus the fin is fixed, and therefore, the rotation of the worm gears is necessary for attaching/detaching the fin and at the same time, the fin is fastened to the board and unlikely to come off by the impact when in use.

Consequently, it is not possible to dislodge the fin in an emergency.

Also according to patent document 10, a tag pin is put in the pin slot and tightened by the club screw, and thus the fin is fastened tightly thereto, but the fin is unlikely to be dislodged and to come off in an emergency.

Further, as to patent document 11, the fin can be attached easily, but its attachment is done by inserting the fin in the obliquely backward direction and if the screw is not used to fix it, there is a possibility that the fin comes off only when a force is applied from a given direction in an emergency.

Consequently, when the fin comes into contact with human body from a variety of unexpected directions, that is, when the fin comes into contact with human body in use of the surfboard, the fin remains almost in the fixed state, and therefore, the contact with human body cannot be dealt with.

As described above, a certain fin attachment structure is desired, which causes the fin to readily come off so as to prevent the damage to human body, that is, which causes the fin to come off the surfboard in a safe manner when in use.

Furthermore, it is originally required for the fin to be attached tightly to the surfboard without abruptly coming off other than in an emergency such as at the time of contact.

Still furthermore, as shown in the prior art, the attachment structure needs to be the one in which the fin can be attached/detached readily for replacement and is fastened securely to the surfboard.

In addition thereto, further when the fin is attached to the board, there will inevitably be a space between the fin and the groove of the board.

That is, if this space is eliminated, at the time of attachment/detachment of the fin, the fin is rubbed throughout the entire groove, thus being hard to be attached or detached.

Therefore, although there inevitably exits a little space, at the time of being attached, this space will cause the rattle of the fin.

Further, in the case of the repetition of the attachment/detachment, or in the case of the use of an arbitrary fin with respect to a board based on the preference of a user, or the like, this space inevitably comes to be larger, and this problem has been required to be properly dealt with.

In particular, as well as regarding a fin that is readily detachable, also regarding a fin to be screwed and fixed, the rattle between the fin and the groove may cause instability at the time of take-off and further may result in the reduction of operability, and some thus solutions will be needed.

For example, conventionally, although paper or vinyl is forced to be filled in the space between the fin and the groove, or a gum tape or a cloth tape is wound around the fin to fill the space, these methods result in a larger space, and additionally it can be difficult to attach or detach the fin.

Thus, some solution methods have been further desired.

The present invention has been devised to solve all such problems well.

The invention according to claim 1 as defined in the present invention is a fin to be attached to a groove in a bottom surface of a surfboard, the fin comprising a hollow part at a side surface of an attachment base portion of the fin,

wherein a ball part is biased outwardly of the hollow part by an elastic member in the hollow part; and

wherein by attachment of the fin in a groove of the surfboard, the ball part in the hollow part of the attachment base portion of the fin is moved into the hollow part against a biasing force from the elastic member, and thus the fin can be detachably mounted in the groove under an elastic compression force, which enables to solve the problems with such construction.

As is the invention according to claim 2, it is preferable to be the fin, wherein there is provided an engaging part including a hook slot for engaging with a fastener including a pin in the groove of the surfboard in one end direction of the attachment base portion of the fin; and wherein there is formed the hollow part in the other end direction of the attachment base portion of the fin and at the side surface of the attachment base portion.

In these cases, as is the invention according to claim 3, it is preferable to be the fin, wherein the hollow part having the ball part biased by the elastic member is formed on both sides of the fin; or as is the invention according to claim 4, it is preferable to be the fin, wherein the hollow part having the ball part biased by the elastic member is formed at least at two or more portions at one side surface.

As is the invention according to claim 5, it is preferable to use the fin, wherein the hollow part is formed of the hollow part going through across both side surfaces of the fin, and there is disposed the elastic member that has the ball part at both end portions of the hollow part and that biases it outwardly of the hollow part.

Furthermore, as is the invention according to claim 6, it is preferable to be the fin, wherein the ball part biased by the elastic member is formed of a plunger, and the plunger is mounted detachably in the hollow part of the attachment base portion of the fin.

In addition, as is the invention according to claim 7, the elastic member may be a coil spring, or as is the invention according to claim 8, at least a part of the ball part may be a spherical body. And further, as is the invention according to claim 9, it is preferable to use the fin, wherein at least the length of the attachment base portion of the fin is smaller than the length of the groove of the surfboard, whereby with any fin, the problems can be solved.

Further, as is the invention according to claim 10, it is preferable to be the fin to be attached to a groove in a bottom surface of a surfboard, the fin at least comprising a hollow part at a side surface of an attachment base portion of the fin,

wherein a non-slip member is mounted in the hollow part; and

wherein the non-slip member is contained at its main body in the hollow part and has a non-slip part at a portion exposed to the outside of the hollow part and sandwiched in a space between the attachment base portion of the fin and the fin attachment groove, thereby to provide non-slip effects.

Alternatively, as is the invention according to claim 11, it is possible to provide the fin, wherein a non-slip member is mounted in the hollow part at a side surface of an attachment base portion of the fin to be attached to a groove in a bottom surface of a surfboard, and further, there is disposed the ball part biased by the elastic member in the same hollow part; and

wherein by its biasing force, the attachment base portion of the fin is attached under elastic compression force, and the non-slip part can prevent a rattle.

In addition, as is the invention according to claim 12, the non-slip member may be detachable, as is the invention according to claim 13, there may be formed in one side surface of the fin the hollow part in which the non-slip member is mounted, as is the invention according to claim 14, there may be formed in both side surfaces of the fin the hollow part in which the non-slip member is mounted, or as is the invention according to claim 15, the fin may have the hollow part in which the non-slip member is mounted, at two or more points.

Possibly, as it the invention according to claim 16, the hollow part may be formed of the one going through across both side surfaces of the fin, and the non-slip member having the non-slip part at both end portions of the hollow part may be mounted in the hollow part.

Furthermore, as is the invention according to claim 17, it is preferable to use the fin to be attached to a groove in a bottom surface of a surfboard,

wherein there are formed the hollow parts at least at two or more portions in the side surface of the attachment base portion of the fin, and the plunger formed of the ball part biased by the elastic member or/and the non-slip member having the non-slip part can be detachably mounted in the hollow part.

Because of such construction, it is possible to provide the fin in which an elastic member allowing the attachment/detachment of the fin is mounted in the fin itself, and this attachment can be done tightly with no rattle.

Thus, the fin can be readily attached to a board, and can be detached.

In this case, at the time of being attached, the fin can be tightly attached by the ball part and the elastic member.

Furthermore, when the tin is brought into contact with human body during surfing, the fin comes off, which enables the suppression of the impact or the damage to the human body to a minimum.

Consequently, it is possible to provide the fin which is easily handled and which has high operational safety.

In addition thereto, according to the invention in claim 1, it is possible to provide the fin which can be easily manufactured, and which has a considerably efficient structure.

Further, besides manufacturing of the fin having such construction, a conventional-type fin can also be improved or modified easily.

Further, according to the invention in claim 2, the present invention is easily applicable to a fin having an attachment structure with a locking member of a pin.

According to the invention in claim 3, because of having the ball part protruding under elastic compression on both sides of the fin, the fin can be fixed in a position elastically compressed with respect to both inner sides in the attachment groove of the board.

According to the invention in claim 4, because of the fact that the hollow part is formed at two or more portions in one side surface of the fin, the fin can be fixed in position under the elastic compression in the well-balanced state in the fin attachment groove of the board.

In addition, according to the invention in claim 5, the elastic member and the bail part can also be mounted in the hollow part having a through hole, which allows the elastic compression with respect to one side, for example, as well as the elastic compression to both sides if required.

According to the invention in claim 6, the present invention can be easily constructed also using various plungers in conformity with the hollow part.

Further, according to the invention in claim 7, an elastic member may employ a coil spring, and thus the attachment stability with the ball part or easy downsizing, or low costs can be achieved.

Furthermore, according to the invention in claim 8, by making a part of the ball part a spherical body in case of, for example, the use in contact with the inner surface of the groove part of the board, point contact can be made and thus its easy attachment/detachment can be achieved.

In addition, if there is formed the recess portion in the groove of the board, a spherical shape can be fitted thereto and thus the attached state can be tightly maintained.

For example, if such spherical shape is formed in the contact direction with the coil spring, it is easy to be fitted in the hollow part at the central portion of the coil-like shape of the coil spring, which thus allows the stability of the attached state.

According to the invention in claim 9, because of the fact that the length of the groove is large, at the time of the attachment/detachment of the attachment base portion of the fin, there is produced a play at both end portions, which thus enables the easy operation.

In particular, in an emergency such as in contact with human body, the fin comes off more readily with this space, which thus enhances safety.

According to each invention in claims 10 and thereafter, instead of the elastic member and the ball part, the non-slip member can be mounted in the hollow part and the space between the fin and the attachment groove of the board can be filled with the non-slip part of the non-slip member, which thus enables the prevention of the rattle when the fin is attached.

Particularly, according to the invention as defined in claims 10 and 11, because of the fact that the non-slip part is formed at the exposed portion of the hollow part, the space between both of them can be filled with the part.

Furthermore, according to the invention in claim 12, the non-slip member is detachable, which thus enables the mounting of an arbitrary non-slip member when required.

Further, according to the invention in claim 13, non-slip effects at one side surface are obtained; and according to the invention in claim 14, non-slip effects on both sides can be obtained.

With the arrangement, the fin can be contacted with the side surface in the groove part of the board with the interposed non-slip part, which thus enables the prevention of the rattle of the fin in the groove part.

In addition, according to the invention in claim 15, because of the fact that the hollow part for mounting the non-slip member is formed at two or more portions, the non-slip members can be mounted at two or more portions and the rattle can be prevented by non-slip effects at two or more portions, which thus enables the stable maintaining of the attached state of the fin.

Furthermore, according to the invention in claim 16, with the through hollow part, the non-slip member having the non-slip part with respect to both inner side surfaces of the groove part can be mounted.

In addition, depending on the shape of the through hole, various shapes of non-slip members can be mounted.

Next, according to the invention in claim 16, the plunger and the non-slip member can be arbitrarily mounted in the hollow part of the attachment base portion of the fin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an example of a fin according to the present invention.

FIG. 2 is a cross-sectional view of an attachment base portion in an example of the fin according to FIG. 1.

FIG. 3 is a view showing an example in the state in which the fin shown in FIG. 1 is attached to a fin box.

FIG. 4 is a cross-sectional view of an attachment base portion of the fin in another example of the fin according to the present invention.

FIG. 5 is a cross-sectional view of an attachment base portion of the fin in another example of the fin according to the present invention.

FIG. 6 is a cross-sectional view of an attachment base portion of the fin in another example of the fin according to the present invention.

FIG. 7 is an enlarged view of a plunger shown in FIG. 6.

FIG. 8 is a cross-sectional view of an attachment base portion of the fin in another example of the fin according to the present invention.

FIG. 9 is a cross-sectional view of an attachment base portion of the fin in another example of the fin according to the present invention.

FIG. 10 is a view showing another example of the fin according to the present invention.

FIG. 11 is a view showing another example of the fin according to the present invention.

FIG. 12 is a view showing an example in the state in which the fin shown in FIG. 10 is attached to the fin box.

FIG. 13 is a view showing another example of the fin according to the present invention.

FIG. 14 is a view showing another example of the fin according to the present invention.

FIG. 15 is a view showing an example of a non-slip member to be detachably mounted in the fin.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a basic example of a fin according to the present invention.

That is, there is provided a ball part 3 biased by a coil spring 2, at the side surface of an attachment base portion 1 of the fin.

These coil spring 2 and ball part 3 are mounted in a hollow part 4 that is formed in the side surface of the attachment base portion 1 of the fin, and the coil spring 2 is disposed in the inner part and the ball part 3 is disposed on the outside.

As a matter of course, for example, a plunger may be used.

In this case, the ball part 3 is at least biased by the coil spring 2 in the state of rather protruding from the side surface of the attachment base portion 1 of the fin to be mounted.

That is, the ball part 3 is biased in the direction of protruding outward by means of the coil spring 2 from the opening of the hollow part 4.

Needless to say, the ball part 3 is disposed to be locatable in a predetermined position using e.g., a crimp at the side edge portion of the hollow part 4 so as not to come out of the hollow part 4 easily.

This drawing shows an example in which the ball parts are disposed two at each side surface of the attachment base portion 1 of the fin.

Because of such construction, when the fin is mounted in a fin box 9, namely fin attachment groove 91 which is provided in the bottom surface of a surfboard, at the time of inserting the attachment base portion 1 of the fin into the attachment groove 91 of the board, the ball parts 3 biased by the coil spring 2 are pressed in the hollow part 4 of the attachment base portion 1 of the fin thereby to be able to be mounted in the groove 91 of the board, and further after attachment, the ball parts 3 are biased by the coil spring 2 and remain in the pressed state in the groove 91 of the board.

Thus, at the time of the attachment of the fin onto a board, the ball parts 3 in the hollow part 4 of the attachment base portion 1 are moved into the hollow part 4 against the biasing force provided by the coil spring 2 thereby to be mounted.

With the arrangement, the attachment base portion 1 of the fin can be maintained in the biased state in the groove 91 of the board, which thus prevents the fin from coming off unexpectedly.

Further, the attachment base portion 1 of the fin can readily be attached or detached against elastic compression force from the ball part 3 biased by the coil spring 2, and thus no special efforts at the time of the attachment/detachment are required.

That is, the fin can be attached by being forcefully fitted into the groove, and further can be detached by being pulled out.

Incidentally, these ball parts 3 are disposed two on each side of the fin, and further the ball parts 3 on both sides are disposed at the opposed positions on both sides so as to be respective pairs.

In these cases, the attachment base portion 1 of the fin which has at least the same length as the attachment groove 91 of the bottom surface of the surfboard or has shorter length than it will suffice.

However, the length in the longitudinal direction of the groove 91 of the surfboard is larger than that in the longitudinal direction of the attachment base portion 1 of the fin; and when the fin is attached, there are spaces in the front-and-rear direction of the groove part 91 each, which thus makes it easy to detach the fin.

Incidentally, when the detachment is like this easy, for example, when an unusual force is applied to the fin during surfing, the fin will come off the groove of the board by this force.

With the arrangement, for example, when the fin hits against human body during surfing, the ball part 3 biased by the coil spring 2 is pressed into the hollow part 4 by this unusual force and the fin comes off, which thus enables the suppression of the damage to the human body to a minimum.

Consequently, even if the fin is unexpectedly brought into contact with the human body, the fin comes off by this force, which thus enables the prevention of injury.

Incidentally, because of the fact that as shown in this drawing, the fin is anchored, for example, at two portions, one pair of the ball parts 3 will come off and the other pair of the ball parts 3 is allowed to provide elastic compression, which thus enables the prevention of the fin from unexpectedly coming off.

Particularly, when a force is applied in one direction e.g., toward the front or toward the rear, the ball parts in a direction most close to the portion where this force is applied are likely to be dislodged, and the fin becomes easily rotatable with the other ball parts as a fulcrum, which thus enables the prevention of the loss of the fin.

Incidentally, as described above, when the fin is mounted in the groove 91 of the board having spaces in the front-and-rear direction of the attachment base portion 1 of the fin, a variety of further advantages are provided; and at the time of normal attachment/detachment, with the above-described spaces, the fin can be fitted in the state of being tilted in the front or rear direction and can be detached in the state of being tilted in the front or rear direction at the time of detachment as well.

Incidentally, as the need arises, there may be provided a spherical recess portion in conformity with the spherical surface of the ball part 3 at corresponding portions in the attachment groove 91 of the board, being biased portions of the ball part 3 at the time when the fin is attached.

With the arrangement, the ball part 3 of the fin can be tightly fitted and secured, and can be positioned precisely to be fixed in place.

FIG. 2 is a cross-sectional view along line A-A of FIG. 1, and a cross-sectional view of the attachment base portion 1 of the fin.

As shown in this drawing, the hollow parts 4 are each formed in opposite positions in the attachment base portion 1 of the fin, the coil spring 2 is mounted in the hollow parts 4, and the ball part 3 is disposed in the opening of the hollow parts 4.

With the arrangement, the ball part 3 for providing elastic compression on both sides of the fin can be disposed in a protruding manner.

Incidentally, the shape of the hollow part 4 just indicates one example, and is not limited to this shape.

In addition, the coil spring 2 is explicitly illustrated, but not limited thereto; and the coil spring 2 has only to be an elastic member 2 that can provide a biasing force in the opening direction, such as a resin material or rubber that has elasticity, or a plate spring or a spring member of other shapes, at least being the one having such elastic compression so as to be capable of fixing the fin in the groove of a board.

Thus, an elastic member having a structure providing oil pressure, hydraulic pressure, or air pressure or other various elastic members capable of providing a biasing force are also the elastic member 2, and any of elastic members 2 capable of providing a biasing force may be used.

Furthermore, the ball part 3 at least has only to be formed to be a protrusion shape at its contact surface with the inner side surface in the groove 91 of a board, and is not necessarily limited to a spherical shape.

Consequently, the shape at least having protruding parts is described to be the ball part 3 in this specification, and this ball part 3 is used in this context.

Furthermore, although in this drawing, the ball parts 3 are disposed at two portions on either side surface of the attachment base portion 1 of the fin, this example is one example, and they may be provided, for example, one on either side, or two or more on either side surface.

Alternatively, not limited to the case where the same number of ball parts 3 is provided on either side, different numbers of them may be provided on both sides.

Further, although in this drawing, the ball parts 3 are provided on both sides at one portion, they may be provided in shifted positions, different from this.

FIG. 3 is a view showing an example in the state where the fin shown in FIGS. 1 and 2 is mounted in a fin box that is the attachment groove 91 of a board.

As is shown in this drawing, the fin can be tightly attached.

FIG. 4 is a view showing another example of the fin according to the present invention, and a view showing an example of the cross-sectional view of the attachment base portion 1 of the fin.

It is a view showing an example in which as in this drawing, there are provided the hollow parts 4 at two portions on either side of the attachment base portion 1 of the fin, and in this hollow part 4, there are formed the coil spring 2 and the ball part 3, biased by this coil spring 2 and protrudingly disposed outwardly of the hollow part 4; and in which particularly, their mounted positions provided on both sides are biased and rather shifted.

In the construction shown in this drawing, the fin can be tightly attached.

FIG. 5 shows the cross-sectional view of another example of the fin according to the present invention, in which there are provided the hollow parts 4 at two points at one side surface and at three points at the other side surface, and there are mounted the coil spring 2 and the ball part 3 in these hollow parts 4.

As in these cases, arbitrary positions and arbitrary numbers of them may be provided each.

FIG. 6 is a view showing another preferred example of the fin according to the present invention.

The construction shown in this drawing is an example in which there is formed the hollow part 4 going through across both side surfaces of the attachment base portion 1 of the fin, and in which a plunger is formed in the hollow part 4.

The plunger has the ball parts 3 each on both sides of a cylindrical-shaped tube and has the coil spring 2 at its central portion, and further each ball is restricted to be in place by e.g., crimping so as not to come out of the cylindrical tube.

With such construction, a biasing force is provided by the ball parts in both side directions.

Incidentally, the diameter of this tube is a diameter which can be inserted in the hollow part 4 of the attachment base portion 1 of the fin, and the width from one ball part 3 to the other ball part 3 is rather larger than the length of the hollow part 4 of the attachment base portion 1 of the fin.

Therefore, by inserting the plunger in the hollow part 4 of the fin, the ball parts 3 biased in both side directions of the attachment base portion 1 of the fin can be disposed.

In this case, the ball parts 3 need to protrude in the side surface direction more than the thickness of the fin.

Incidentally, with such construction, the plunger can be mounted detachably in the hollow part 4 of the fin, and can be attached if required, or can be detached and used.

In addition, the replacement with an arbitrary plunger having elasticity or a ball shape which is most suitable to a user can be made, and the plunger can be easily replaced at the time of e.g., the occurrence of defects.

Incidentally, the greatest advantage exists in that by forming the hollow part 4 in the attachment base portion 1 of the fin used, a plunger can be attached without restriction to a general-purpose fin.

Thus, a variety of fins can be easily modified into the fin according to the present invention.

FIG. 7 is an enlarged view of the plunger shown in FIG. 6, in which plunger there are provided on both sides of the cylindrical-shaped tube the ball parts 3, there is disposed the coil spring 2 at the central portion, and further, the ball parts 3 are restricted in place, for example, by crimping so as not to come out of the cylindrical tube each.

In this case, as mentioned above, various elastic members 2 may be used instead of the coil spring 2, and there has only to be the ball part 3 having protruding parts.

Incidentally, the diameter of this so-called plunger may be arbitrary, and the plunger has only to be of the diameter in accordance with the diameter of the hollow part 4 of the attachment base portion 1 of the fin.

In addition, the length of the plunger tube has only to be substantially the same as the thickness of the fin or to be shorter than this thickness, and at least the ball parts 3 has only to be in the protruding state under elastic force from one side surface or both side surfaces at the time of being mounted in the hollow part 4.

The plunger, insofar as it could be disposed in this way, for example, may have the tube longer than the thickness of the fin.

FIG. 8 is a cross-sectional view of the attachment base portion 1 showing another example of the fin according to the present invention, and a view showing an example in which there are formed the hollow parts 4 having bottoms each at both sides of the fin, and a plunger having the ball part 3 only on one side is mounted in each hollow part 4.

As to the construction shown in this drawing, a detachable plunger having the ball part 3 biased by the coil spring 2 is used, the plunger has the ball part 3 only on one side, and the ball part 3 is biased by the coil spring 2.

Even if it is constructed in this way, the plunger can be detachably mounted, and it can be replaced by an arbitrary plunger if needed.

FIG. 9 is a view showing an example in which in the construction shown in FIG. 8, positions in which the hollow parts 4 of the attachment base portion 1 of the fin are formed are changed.

This drawing shows an example of using the As is shown, it is a view showing an example in which the hollow parts 4 are formed being staggered each other at four portions at one side surface and at three portions at the other side surface.

This drawing shows an example of using the same plunger as that of FIG. 8.

FIG. 10 is a view showing another example of the fin according to the present invention.

The fin showing in this drawing is a fin in which a pin is provided in the fin attachment groove 91 of a fin box in the bottom surface of a surfboard, and a hook slot of the fin is hooked on this pin, thereby to attach the fin in the fin box.

In this case, although for example, in the conventional fin, further the fin is fastened and fixed in place using other fasteners, for example, screws or other locking parts, in the construction shown in this drawing, there are provided in the opposite direction of the hook slot of the attachment base portion 1 of the fin, the hollow part 4, the elastic member 2 such as a coil spring and the ball part 3, and the fin is mounted in place elastically pressed in the fin box by the biased ball part 3.

In this case, a plunger may be mounted in the hollow part 4, or a plunger that is detachably mounted in the hollow part 4 may be configured.

With such construction, the fin can be readily attached or detached, and further, when a predetermined force is applied in an emergency, the fin will come off.

Incidentally, although the fin shown in this drawing is shaped to be a hook slot at one end of the attachment base portion 1 of the fin, it may be the one having the other fastener for screwing, for example, and possessing this structure at the other end portion of the fin.

Furthermore, it may be of construction in which there is provided at the attachment base portion of the fin, a locking part such as a pin member, and there is formed in the fin box or the board main body, a groove part composed of a conducting path that conducts the pin so as to be able to move to a predetermined position.

Incidentally, although according to the present invention, the attachment base portion 1 of the fin is described to be attached to the fin box 9, that is the fin attachment groove 91 which is formed at the bottom surface of the surfboard, the present invention is also applicable to, for example, the one in which the groove 91 is formed in the bottom surface of the surfboard and the fin is directly attached.

Therefore, the construction according to the present invention, other than the one in which a fin box is provided, is applicable specifically to the one in which the groove 91 is formed directly in the bottom surface.

FIG. 11 is a view showing another example of the fin according to the present invention, and a view showing an example in which there are provided the hollow part 4, the elastic member 2 and the ball part 3 at three portions at one side surface of the fin.

Incidentally, as the elastic member is mounted in the hollow part 4, it is not shown in detail in the drawing.

As is in this drawing, the hollow parts 4 and the like of the attachment base portion 1 of the fin is formed at arbitrary portions or arbitrary numbers of them.

FIG. 12 is a view showing an example when the fin shown in FIG. 10 is attached to the fin box, in which the hook slot of the attachment base portion 1 of the fin is hooked on the pin of the fin box, and further the fin is fixed in position elastically pressed in the fin box by the hollow part 4, the coil spring 2 and the ball part 3 at the other end of the fin.

In this case, for example, when the fin is lifted up from the rear, as indicated by the chain line, the fin is released from elastically pressed position by the ball part 3 and rotated with the pin on which the hook slot is hooked as an axis thereby to come off.

On the contrary, in this state in which the hook slot is hooked on the pin and further the other end of the fin is pressed in the groove 91 of the fin box, the fin can be readily attached.

Furthermore, when an unexpected force is applied from the rear of the fin, one end of the attachment base portion 1 of the fin is released against the elastic compression force from the ball part 3 and the rear portion of the fin comes off the fin box, but the fin remains in the state of being attached to the board as it is with the hook slot hooked on the pin.

That is, although the rear portion of the fin is pulled out of the groove 91, the pin is still engaged in the hook slot in the front of the fin. Thus, the fin is caught by the board in the state of being rotated in the forward direction.

That is, in the contact state from the rear of the fin in which particularly the fin is much likely to be in contact with human body, that is in the state in which a force from the rear of the fin is applied, the fin is released from being caught by the ball parts, and the force from the rear of the fin is converted into rotational force with the pin hooked in the hook slot of the fin as an axial center.

Consequently, even if the fin hits against the human body, the fin comes off, turns forward and backward, and thus the contact state with the human body can be avoided, which enables the alleviation of impact without damage to the human body.

As described above, although the fin according to the present invention is variously usable and extremely easy to use, it is preferable that there is formed, for example, a fin in which there are provided only on one side surface of the attachment base portion 1 of the fin the hollow part 4, the elastic member 2 such as a coil spring and the ball part 3.

For example, it is preferable to be of construction in which there is provided on one side surface a member having elasticity such as rubbers or the like, and at least with which one side surface of the attachment portion of the fin is inserted and supported in the fin box; and in which the attachment base portion of the fin is fixed in position elastically pressed by the ball part 3 on the other side surface.

In addition, it is preferable that there is formed a recess portion in which the ball part is fitted in a position on the inner surface of the fin box, that is the fin attachment groove 91, provided at the bottom surface of the surfboard, which position corresponds to that of the ball part 3 disposed in the hollow part 4 of the attachment base portion 1 of the fin.

With that, the ball part is tightly fitted therein, and thus more tightly mounted state can be maintained.

On the other hand, in an emergency or at the time of detachment, it can be detached.

Further, even in the construction of this attachment base portion of a fin or in a normal composition, in many cases, the fin is moved.

Thus, as shown in FIG. 13, it is preferable that there is formed in the attachment base portion 1 of the fin the hollow part 4, and a non-slip member 5 is mounted in the hollow part 4.

That is, the non-slip member 5 having a non-slip part 51 at the portion protruding outward from the hollow part 4 at the portion protruding and the non-slip part 51 provides non-slip effects between the attachment base portion 1 of the fin and the corresponding surface of the groove 91 part for attachment of the fin, which thus enables the prevention of e.g., rattle of the fin.

Therefore, the hollow part 4 is formed in the attachment base portion 1 of the fin, and the non-slip member 5 having the non-slip part 51 in a position protruding outward from the hollow part 4 when being mounted in this hollow part 4 is mounted. Thus, the fin can be easily brought into tightly attached state.

In this case, the hollow part 4 in which the non-sip member 5 is to be mounted has only to be of the same construction as that of the hollow part 4 in the attachment base portion 1 of the fin in which plungers are to be mounted, and it may be, for example, besides a through hollow part of a cylindrical tube shape, the one having its bottom, the one formed to be a hollow part of a triangular prism, a quadrangular prism or a polyhedral prism, or the one having a hollow part of other arbitrary shapes.

At least, this hollow part 4, as in the case of the shape in which plungers are mounted and the ball part can be protruded, has only to be of a form in which the non-slip member 5 can be mounted and further the non-slip part 51 can be protruded.

With the construction, the non-slip member 5 can be easily mounted on the fin, and thus the rattle of the fin can be prevented.

Furthermore, by making the non-slip member 5 detachable, the non-slip member 5 having a size most suitable for providing non-slip effects depending on the conditions or in the relation between a board and a fin.

The non-slip member 5 according to the present invention has only to be the one which can be mounted in the hollow part 4 and which protrudes the non-slip part 51 at the time of being mounted, and has only to be the one in which the non-slip part 51 is positioned between the attachment base portion 1 of the fin and the fin attachment groove 91 and can prevent the rattle through frictional resistance of the non-slip part 51 between both of them.

In addition, more desirably, the non-slip member 5 is detachable in the hollow part 4, and can be replaced by the non-slip member 5 most suitable for preventing the rattle.

Furthermore, the non-slip member 5 can also be set to be of various sizes, for example, the non-slip part 51 can be set to be of a variety of arbitrary areas or shapes, and also the non-slip member 5 with various structures of the non-slip part 51 will suffice.

For example, the non-slip part 51 may be the one having a variety of arbitrary irregularities, the one having an adhesive member, or the one that is made of a member having elasticity.

For example, the non-slip part 51 may be formed of a resin material having elasticity, or the surface of this resin material is formed in irregular shapes.

In addition, the non-slip part 51 of the non-slip member 5 has only to be constructed so as to be in a position rather protruding from the hollow part or in a position substantially at the end surface portion of the hollow part 4 at the time of mounted in the hollow part 4.

At least, the non-slip part 51 is mounted in the space between the attachment base portion 1 of the fin and the fin attachment groove 91 so as to be sandwiched between both of them, which has only to enable the prevention of the rattle.

In this case, the non-slip member 5 may be mounted on both sides of the attachment base portion 1 of the fin or mounted only on one side; or further, the hollow part 4 is formed of the through hollow part 4, and the non-slip member 5 having the no-slip part 51 at both end surface portions is mounted, which has only to produce non-slip effects on both sides.

At least, the non-slip member 5 is mounted in the hollow part 4 that is formed in the attachment base portion 1 of the fin, and the non-slip member 5 having the non-slip part 51 at the portion exposed to the outside of the hollow part 4 and sandwiched in the space between the attachment base portion 1 of the fin and the fin attachment groove 91 produces non-slip effects, which has only to enable the prevention of the rattle at the time of attachment of the fin.

FIG. 14 is a view showing an example in which the hollow parts 4 are formed at two portions in one surface of the attachment base portion 1 of the fin, the non-slip member 5 having the non-slip part 51 is mounted in these hollow parts 4, and the non-slip part 51 is protruded from the side surface of the base portion 1.

With such construction, the space of the side surface of the fin can be made much smaller, which thus enables the prevention of the rattle.

In particular, in fins generally used, can be provided a fin in which the hollow part 4 is formed in the attachment base portion 1 of the fin, and further the non-slip member 5 having the non-slip part 51 is mounted in the hollow part 4, which thus enables the easy prevention of the rattle.

In addition, by employing the detachable non-slip member 5, the optimum non-slip member 5 can be mounted depending on the daily state, the state of a board and the like.

FIG. 15 is a view showing an example of the detachable non-slip member 5 having the non-slip part 51 at both ends.

A non-slip member of various shape structures can be formed by e.g., the change of the size of the non-slip surface, or the change of the material or shape of the non-slip part, or the change of the length of the base portion providing connection therebetween, the degree of non-slip effects can be arbitrarily set, and the non-slip member can be implemented properly in the most suitable construction with respect to every fin.

Consequently, a fin having a non-slip member of extremely high applicability can be provided as well.

EXPLANATION OF REFERENCE NUMERALS

-   1: attachment base portion of fin -   2: elastic member (coil spring) -   3: ball part -   4: hollow part -   5: non-slip member -   51: non-slip part -   9: fin box -   91: fin attachment groove

INDUSTRIAL APPLICABILITY 

1. A fin to be attached to a groove in a bottom surface of a surfboard, the fin comprising: a hollow part 4 at a side surface of an attachment base portion 1 of the fin, wherein a ball part 3 is biased outwardly of the hollow part 4 by an elastic member 2 in the hollow part 4; and wherein by attachment of the fin in a fin attachment groove 91 of the surfboard, the ball part 3 in the hollow part 4 of the attachment base portion 1 of the fin is moved into the hollow part 4 against a biasing force from the elastic member 2, and thus the fin can be detachably mounted in the groove under elastic compression force.
 2. The fin according to claim 1, wherein there is provided an engaging part for engaging with a fastener in the fin attachment groove 91 of the surfboard in one end direction of the attachment base portion 1 of the fin; wherein there is provided the hollow part 4 in the other end direction of the attachment base portion 1 of the fin and at the side surface of the attachment base portion
 1. 3. The fin according to claim 1, wherein the hollow part 4 having the ball part 3 biased by the elastic member 2 is provided on both sides of the fin.
 4. The fin according to claim 1, wherein the hollow part 4 having the ball part 3 biased by the elastic member 2 is provided at least at two or more portions at one side surface.
 5. The fin according to claim 1, wherein the hollow part 4 is formed of the hollow part 4 going through across both side surfaces of the fin, and there is provided the elastic member 2 which has the ball part 3 in both end directions of the hollow part 4 and which biases it outwardly of the hollow part
 4. 6. The fin according to claim 1, wherein the ball part 3 biased by the elastic member 2 is formed of a plunger and the plunger is mounted detachably in the hollow part of the attachment base portion 1 of the fin.
 7. The fin according to claim 1, wherein the elastic member 2 is a coil spring.
 8. The fin according to claim 1, wherein at least a part of the ball part 3 is a spherical body.
 9. The fin according to claim 1, wherein at least the length of the attachment base portion 1 of the fin is smaller than that of the groove of the surfboard.
 10. A fin to be attached to a groove in a bottom surface of a surfboard, the fin at least comprising a hollow part 4 at a side surface of an attachment base portion 1 of the fin, wherein a non-slip member 5 is mounted in the hollow part 4; and wherein the non-slip member 5 is contained at its main body in the hollow part 4, has a non-slip part 51 at a portion exposed to the outside of the hollow part 4 and is sandwiched in a space between the attachment base portion 1 of the fin and the fin attachment groove 91, thereby to provide non-slip effects.
 11. The fin to be attached to a groove in a bottom surface of a surfboard according to claim 1, the fin at least comprising a hollow part 4 at a side surface of an attachment base portion 1 of the fin, wherein a non-slip member 5 is mounted in the hollow part 4; and wherein the non-slip member 5 is contained at its main body in the hollow part 4, has a non-slip part 51 at a portion exposed to the outside of the hollow part 4 and is sandwiched in a space between the attachment base portion 1 of the fin and the fin attachment groove 91, thereby to provide non-slip effects.
 12. The fin according to claim 10, wherein the non-slip member 5 is detachable.
 13. The fin according to claim 10, wherein there is provided in one side surface of the fin the hollow part 4 in which the non-slip member 5 is mounted.
 14. The fin according to claim 10, wherein there is provided in both side surfaces of the fin the hollow part 4 in which the non-slip member 5 is mounted.
 15. The fin according to claim 10, wherein the hollow part 4 in which the non-slip member 5 is mounted is provided at two or more portions.
 16. The fin according to claim 10, wherein the hollow part 4 is formed of the hollow part 4 going through across both side surfaces of the fin, and the non-slip member 5 having the non-slip part 51 in both end directions of the hollow part 4 is mounted in the hollow part
 4. 17. The fin to be attached to a groove in a bottom surface of a surfboard according to claim 1, wherein there is provided the hollow part 4 at least at two or more portions in the side surface of the attachment base portion 1 of the fin, and the plunger formed of the ball part 3 biased by the elastic member 2 or/and the non-slip member 5 having the non-slip part 51 can be detachably mounted in the hollow part
 4. 